Mesozoic Vertebrates Blog

Sunday, 27 January 2013

Recently, Richard Butler and colleagues, including myself, published a short paper describing only a part of a tail of a basal sauropodomorph dinosaur, a "prosauropod", from the Early Jurassic (some 185 million years ago) of South Africa. "So what?", you might think. Well, of course it is not just any random basal sauropodomorph tail, but there is something unusual about it: When we excavated the specimen, probably of the genus Massospondylus, in the Elliot Formation of Eastern Cape Province in 2008, we noted that the tail of the animal ended in a strange mass of bone. After preparation it turned out that the end of the tail had obviously been severed while the animal was still alive, and it survived the injury, at least for some time, as evidenced by reactive bone growth around the point where the tail had been cut off.

The corpus delicti: an injured tail.

Thus, the interesting question of course is: What happened to the animal? And how did it affect it in life?
There are several possibilities how this individual might have lost its tail. One is trampling, that a cogeneric simply stepped on the tail, causing an injury that got infected and finally led to the end of the tail falling off. However, given the type of injury and reactive bone growth, this seems rather unlikely. So, the second possibility is that the injured tail is evidence of an unsuccessful attack by a predatory animal, most probably a predatory dinosaur. This is the scenario that we considered more likely, and it has some interesting implications. First of all it indicates that Early Jurassic predatory dinosaurs were active predators, and not merely scavengers, and that they did target large animals and not only small prey. This is somewhat surprising, given that the largest known predatory dinosaurs from the Elliot Formation are about the same size as the Massospondylus specimen attacked, and they were rather gracile animals. On the other hand, the fact that the attack was unsuccessful indicates that Massospondylus had means to survive an attack by a predatory dinosaur, even after having received a serious wound, such as loosing a third of its tail. Maybe the animal got away, despite the injury, or maybe these basal sauropodomorphs lived in groups and helped each other when attacked. As you can see, such a specimen can lead to interesting thoughts. However, one should keep in mind that the actual FACT that we have is an injured tail - everything else becomes more and more speculative.

This leads me to another topic: If you look into the newspapers (be it on paper or online) to look at science news, you might get the idea that everything reported there is groundbreaking, shaking the foundations of our current knowledge. So, is this the case with our new study as well? Rather not; this observation tells us certainly more about how journalism works than how science works. Now and then there really are new discoveries and new studies that challenge accepted views, but these are rather exceptional events. However, the journalist must sell the story to her/his readers and thus has the tendency to hype the significance of the study reported, and, since we are all under pressure to get public attention in order to be competitive for the limited resources allocated to science, many scientists have learnt to play this game as well. But this is not the nature of science!

The world as seen by science: looking for the next pieces.

Most scientists I know do not start an investigation with the aim to overthrow accepted knowledge, but rather out of curiosity of what they might find. Science is like an enormous puzzle; there sure are some key pieces, but to get the entire picture, you also need the rather insignificantly looking pieces as well, and most of science is working on such pieces. Thus, although there are of course some studies that might be more important than others, there is no scientific investigation that is completely useless - even negative results can tell us something. This is something to keep in mind next time you read about science that might, at first, seem insignificant - such as a description of an injured tail in a basal sauropodomorph: Scientists are looking for another piece of the puzzle to complete our picture of the world. However, the analogy with the puzzle is also only partially correct: What often happens is that the discovery of one piece makes you realize that even more others are still missing...

Monday, 5 November 2012

That's the (inofficial) story behind the name of our recently described new rhynchocephalian Oenosaurus muehlheimensis. When the remains of this animal, which only consist of a crushed skull that was exposed in palatal view, and both mandibles, were found at the Schaudiberg quarry at Mühlheim, the quarry owners and the scientists working with them were first at a loss as to what animal this was. Anybody whom they showed it to had ever seen anything like that before, and my first guess, when shown photos of the skull in palatal view, was that it might be a chimeran chondrichthyan. Later we wondered whether it might represent a late surviving rhynchosaur, with the typical maxillary tooth battery that these animals possess. Only when I examined the mandibles, finally recognition dawned: these elements, with their high coronoid processes, enlarged mandibular foramen and convex articular surface, clearly indicated that we were dealing with a sphenodontian (=rhynchocephalian).

Preparation and careful examination and comparison of the skull confirmed this identification. Oenosaurus really represented a rhynchocephalian, though with a dentition as it has never been described before in a tetrapod. The dentition consists of massive tooth plates, which, under closer inspection, seem to be made up of hundreds or thousands of fused individual teeth, with small internal cavities and concentric arrangements of dentine layers around them. That's what it looked like when examining the tooth plates under the microscope, and our first interpretation was that these plates indeed represented simply fused individual teeth, possibly including several tooth generations, as in the tooth batteries of some ornithischian dinosaurs. Given that rhynchocephalians usually do not show tooth replacement, this would have been weird enough, but then we made a computer tomography of the tooth plates. The results showed no evidence of replacement teeth, but apparently continously growing dentine tubules that were fused into a single structure towards the surface and sometimes even showed branching patterns. A literture survey revealed that similar structures are basically only found in chimeran chondrichthyans and lungfishes, where this tooth tissue is called osteodentine or petrodentine.

Right mandible of Oenosaurus in lateral view.

Rhynchocephalians are an ancient lineage of lepidosaurian reptiles, the group that modern lizards and snakes also belong to. However, in contrast to the latter, which are currently represented by several thousand species, only two species of rhynchocephalians survived to the present day, both in the genus Sphenodon. This genus, commonly named the Tuatara, is currently restricted to s few islands off the coast of New Zealand, where these animals have found their last refuge. Since Sphenodon belongs to such an ancient lineage and also shows some rather primitive looking features, it is often considered a living fossil, and was consequently used frequently in studies relating to allegedly ancestral conditions for modern lizards, also in recent times.

Photo of the rather sympathetic looking Sphenodon, the only recent rhynchocephalian (courtesy Helmut Tischlinger).

However, palaeontological research in recent decades had already shown that many of the alledgedly primitive characters of Sphenodon are actually secondarily derived, and that rhynchocephalians were a diverse and successfull branch of the lepidosaurian tree at least in the early to mid-Mesozoic. Nevertheless, rhynchocephalians kept their status as "evolutionary loosers": since they seemed to have been inferior to lizards in the adaptability, they were doomed to dwindle and almost vanish. Only recently, research by Hugo Reynoso, Sebastian Apesteguía and Marc Jones, among others, has forcefully shown that rhynchocephalians were not only systematically, but also ecologically diverse and highly successful. With its extremely modified tooth plates, indicating a crushing dentition, an adaptation previously unrecorded in rhynchocephalians, Oenosaurus underlines this high evolutionary plasticity of the group and thus seriously calls into question the idea of their inferiority. This is another nice example that judging groups of animals by their recent representatives alone might greatly underestimate their true nature and potential, and that the very concept of a "living fossil" might be seriously flawed. The whole story can, though admittedly always still incomplete, only be told by incorporating the fossil record.

The 72nd
annual meeting of the Society of Vertebrate Paleontology was held in Raleigh, North
Carolina, USA (October 17 – 20, 2012). More than 1,000 attendees interested in
various facets of the discipline of vertebrate paleontology - such as the
biology of long-extinct dinosaurs - presented and discussed their latest scientific
advances.

For instance, we now have new clues about one of the biggest enigmatic events
during evolution of life: the origin of jaws. A recent study shows that the
evolutionary change from jawless to jawed vertebrates can be clearly traced by
400 million years old, transitional fossils.

The
Mesozoic Vertebrates Group at the Bayerische Staatssammlung für Paläontologie
und Geologie in Munich, Germany, was involved as well in crucial contributions
to diverse aspects of reptilian evolution. Almost all members presented and
discussed their recent research results.

We
addressed the question of how to explain the diverse neck lengthening in
dinosaurs?
Christine Böhmer and colleagues provided a first-time glimpse at genetic
expression during the embryonic development of long-extinct fossil dinosaurs in
order to understand the evolution of neck length.
A re-evaluation of phytosaurs (extinct crocodile-like reptiles) from Central
Europe by Richard Butler and colleagues gave new insights into the ancient
ecosystem of these animals.
On the trail of the famous german paleontologist Ernst Stromer. Serjoscha Evers
and colleagues reported on an enigmatic theropod dinosaur from northern Africa.
As a result of the work by Martin Ezcurra and colleagues we have new
information about the Triassic-Jurassic mass extinction event (about 200 millon
years ago) that had a deep impact on the early evolution of theropod dinosaurs.
Christian Foth and colleagues illustrated their results on the evolutionary
history of the Mesozoic flying reptiles, the Pterosauria.
Albert Prieto-Marquez and colleagues talked about potential triggers for the
diversity peak of megaherbivore dinosaurs in the Late Cretaceous.
Oliver Rauhut and his colleague Diego Pol presented a new theropod dinosaur
from Patagonia, Argentina. The skeleton of this huge animal is the most
complete tetanuran from the early Middle Jurassic.
Roland Sookias and colleagues talked about trends in tetrapod body size
evolution and concluded that biological limits , not environmental limits,
become increasingly limiting as larger sizes are reached.

In all, the
international meeting was a great success not only concerning the promotion of
excellent research by the Mesozoic Vertebrates Group but also in encouraging collarboration
with associates from all over the world.

Thursday, 26 July 2012

Although snakes might not be the favourite critters of most people, these animals are certainly among the most amazing land-living vertebrates today. Legless, with greatly elongate bodies, and astonishing feeding adaptions, such as venomous fangs and hyperextensible jaws, snakes are also among the most successfull vertebrate groups, with almost 3000 species known today. However, the fossil record of snakes is still rather poor, and this is especially true for their origin. Thus, the evolution of the remarkable anatomical adaptations of snakes, and their functional and ecological context remain enigmatic.

Skull reconstruction of Coniophis and a modern snake (modified from Longrich et al. 2012, and Pough et al. 2004)

Nick Longrich and colleagues have now published new material of the latest Cretaceous snake Coniophis from North America that has some bearing on these questions. Although the taxon has been known for 120 years, only isolated vertebrae had been described so far. Longrich and colleages now described skull remains and additional vertebrae that throw new light on the anatomy and ecology of this early snake. The new remains show that the skull of Coniophis had the typical hook-shaped teeth and intramandibular joint of snakes, which help to expand the gape to swallow larger prey. However, the upper jaw was firmly attached to the other skull bones, much as in lizards, and thus not allowed the extensic movements between differetn skull bones that we see in modern snakes. Thus, Coniophis presents an interesting mosaic of characters that helps understanding how the feeding apparatus of snakes evolved.
However, one other aspect of the new paper I find somewhat more problematic. There is a long-standing debate whether snakes evolved from aquatic or land-living ancestors, and, if the latter was the case, whether these animal were terrestrial, tree-living, or burrowing. On the basis of the environment that Coniophis was found in and the features of the vertebrae, Longrich and colleagues deduce that this was a land-living and most probably burrowing animal. So far so good, but the next step goes further: on the basis of these findings, the authors suggest that the ancestor of snakes was probably terrestrial and burrowing. However, Coniophis comes from the Maastrichtian stage of the Cretaceous, some 65 million years ago, whereas the oldest known certain snakes date back to the late Early Cretaceous, some 100-120 million years ago. Now, that leaves us with two possibilites: First, the apparently primitive morphology of Coniophis is actually secondarily derived and has evolved from a "typical" snake, which seems unlikely. Second, Coniophis is a member of a primitive lineage of snakes which, according to its relationship with more dervied snakes, must reach back to the late Early Cretaceous at the least and thus have a ghost lineage (an evolutionary lineage without fossil record) of at least 35 million years. Given the fallacies of the fossil record in general and the poor fossil record of snakes in particular, the second explanation seems much more likely, and is also the one favoured by Longrich and colleagues. However, 35 million years are a very long time; indeed, this is more than half the length of the entire Cenozoic, the "age of mammals". The interpretation that a randmom member of such a long-lived evolutionary lineage that lived such a long time after its origin represents the original ecology of the clade is maybe not impossible, but nevertheless rather questionable. Assuming we would not have any good fossil record for either group, would you assume that elephants originated from marine animals, because their closest relatives, the Sirena, are marine today? Thus, although Coniophis provides exciting new insights into the evolutionary history of snake anatomy, I would be careful in interpreting its importance for the question of the ecological origin of snakes.

Longrich, N.R., Bhullar, B.-A.S. & Gauthier, J.A. 2012. A transitional snake from the Late Cretaceous period of North America. Nature, published online.

Wednesday, 11 July 2012

There are certain taxa of Mesozoic vertebrates that every palaeontologist knows. One of these is certainly Lepidotes. Originally named by the great Louis Agassiz in 1832 based on a fish from the Early Jurassic of south-western Germany, the genus soon became a "wastebasket" for any remain of a Mesozoic fish with thick bony scales. Thus, there is a plethora of Mesozoic fish species referred to the genus Lepidotes, spanning the time from the Early Jurassic to the latest Cretaceous, or a time span of some 130 million years. Many of the fishes that were not referred to Lepidotes became species of Semionotus, another wastebasket taxon. Disentangling this mess seemed a task that no palaeontologist was willing to tackle.

Yes, this is a Lepidotes! Lepidotes gigas from the type horizon of the genus, the Posidonia Shale, at the BSPG.

Lepidotes and the other bony-scaled fishes represent a number of primitive lineages that were common in the Mesozoic, but dwindled to a mere nine or ten species today, which seem insignificant in comparison to the more than 25,000 species of the modern ray-finned fishes (teleosts). Nevertheless, these few species are the only available evidence for the evolutionary history that led to the origin of the modern fishes - with the exception of the fossils. However, interpreting the evolution of fishes in the Mesozoic is severely hampered by the lack of hypotheses on the interrelationships of many of the important lineages. Referring every second fish with thick bony scales from Mesozoic deposits to one of two genera certainly doesn't help in this respect. Lepidotes and several other Mesozoic fishes - most notably the almost as inflated Semionotus - are usually included in a group called Semionotiformes - which is widely used, despite the fact that most experts in fossil fishes recognized that semionotiforms are not a natural group.

This was the situation when Adriana López-Arbarello started with a project on semionotiform fishes in 2006. The German Research Foundation (DFG) financed this impossible seeming task, first for two years, but with extensions of anther two years. And thus Adriana went to work, logically first with revising materials referred to Lepidotes and Semionotus, starting with the original species of these two genera. Thus, over the years, she and her co-workers published new descriptions of the type species of Semionotus, a redescription of Neosemionouts, and coined new names for two other groups of species that were originally referred to Lepidotes, Scheenstia and Macrosemimimus. She further studied new semionotiforms, three of which are already published, Tlayuamichin from the Cretaceous of Mexico, Sangiorgioichthys sui from the Triassic of China and Lepidotes pankowski from the Cretaceous of Morocco. But, apart from this taxonomic work, she mainly used the detailed studies of many specimens and the visits to collections to collect data for an analysis of the interrelationships of these fishes.

This analysis was now published in the journal PLoS One. It represents the largest and most explicit phylogenetic analysis of semionotiform fishes. Adriana found many interesting results, most importantly the division of semionotiforms into two separate lineages, one of them including Semionotus and its relatives and the other Lepidotes and the fishes more closely related to this genus. This might still not be too surprising - but the latter lineage was found to lead to the modern gars, and the former includes a group that was so far considered to be an own lineage of Mesozoic fishes, the macrosemiids. Based on these relationships, Adriana decided to use the name Lepisosteiformes for the Lepidotes-gar lineage (Lepisosteiformes being the group that modern gars belong to) and restrict Semionotiformes for the Semionotus-macrosemiid lineage. Both lineages were united in the group Ginglymodii.

The interrelationships of ginglymoidian fishes according to López-Arbarello (2012).

These results have far-reaching implications. For one thing, ginglymodians are a more diverse group than previously recognized, being represented by many different lineages with often long ghost lineages (extensions of the lineage for which fossil evidence is still missing), indicating that these fishes were also taxonomically more divers. Furthermore, ginglymodian fishes were ecologically divers, and the recognition of Lepidotes and its kin as fossil relatives of modern gars helps to understand the evolutionary history of these fishes.

So, Adriana has made an important step in her studies of the interrelationships of Mesozoic fishes that stand at the base of modern groups. Does that mean that everything is known now about the evolution of the Ginglymodii, and she can turn to other things? Certainly not, Adriana's work represents only a beginning. There are many more species of Lepidotes and Semionotus to be revised and to be included in the analysis of the interrelationships, and detailed studies of other groups of Mesozoic fishes are necessary to further elucidate the origin of modern clades of bony fishes. However, her paper presents a first reference frame for such studies. It includes a wealth of anatomical and character data that are of importance for the interpretation of the interrelationships of Mesozoic fishes and presents hypotheses of interrelationships that are sure to spark discussion and renewed interest in these groups in ichthyologists. Thus, it will provide fertile ground for future studies of the role that Mesozoic fishes play in our understanding of the origin of our modern vertebrate diversity.

Monday, 9 July 2012

Vertebrate paleontologists often have to deal with fragmentary remains; complete skeletons, such as that of Sciurumimus, are extremely rare. The vast majority of specimens in vertebrate palaeontology consist of isolated teeth or bones, or often even only parts of these. Thus, palaeontologists are often faced with the challenge of interpreting these fragments, identifying their identity and evaluating their evolutionary or biogeographic significance. Many of us have published on such remains and sometimes have drawn far-reaching conclusions on the basis of a few isolated bones or teeth. I myself am certainly guilty of this, having announced the first dromaesaurid (sickle-clawed dinosaur, a relative of the famous Velociraptor) from the southern hemisphere on the basis of a tooth and a few foot bones, or having described the first Jurassic tyrannosauroid from Europe on the basis of a single ilium. Of course, claims on the basis of such material are often contested. A good example for this are dinosaur remains from the Cretaceous of Australia, which almost all consist of isolated bones, and which have been interpreted very differently by different scientists.

Recently, my Argentinean colleagues Martín Ezcurra and Federico Agnolín re-interpreted a distal end of a tibia (the shin bone) of a small predatory dinosaur from the Middle Jurassic of England as one of the oldest representatives of the abelisauroids, a group of peculiar predatory dinosaurs which are mainly known from the southern hemisphere. This specimen would thus not only be one of the oldest representative of abelisauroids, but also the oldest record of this group from the northern hemisphere. This interpretation obviously had far-reaching implications for the evolution and biogeography of this dinosaur group, which were clearly lined out by Ezcurra & Agnolín.

Example of an abelisauroid: Carotaurus sastrei (by Nobu Tamura)

Since I am currently working on a Middle Jurassic abelisaurid from Argentina - which Diego Pol and me recently published as Eoabelisaurus mefi - I was, of course, very interested in this re-interpretation of the small theropod (the predatory dinosaurs) specimen from England. However, reading the article, I was unconvinced of the interpretation presented by Ezcurra and Agnolín. Thus, I got out my photographs of predatory dinosaurs that I took in many different collections over the years, asked a few colleagues for images of other specimens that I thought might be of interest (which many of them provided; special thanks here to Roger Benson, Lindsay Zanno, Jacques Gauthier and Brooks Britt), and then wrote a short article arguing against the interpretation presented by Ezcurra & Agnolín. In this article, I could show (I hope) that the characters used by Ezcurra & Agnolín to refer the specimen to abelisauroids have a wider distribution within theropods, and that the bone in question can thus only be identified as an indeterminate predatory dinosaur.

The bone of contention: distal end of a shin bone of a small predatory dinosaur.

So, having thus publicly disagreed with my colleague Martín Ezcurra, does that mean that I think that he is a poor anatomist? Certainly not; on the contrary, I value Martín's detailed anatomical observations very highly and generally think that he does excellent work! Indeed, a few months ago, Martín started working as a PhD student here at Ludwig Maximilian University in Munich with my friend and colleague Richard Butler, and in all things theropod, I often consult with him. The article by him and Federico Agnolín is also not an example of poor science. The two presented testable characters for the referral of the element in question to abelisauroids, which only made it possible for me to criticise their work. Thus, this is proper scientific procedure: You present your data and the hypothesis derived from it. This hypothesis is then out there to be tested in the light of new data or other observations, which is exactly what I did in this case: I presented observations that showed that their data is not sufficient to support their conclusions. Only by putting the data and your ideas on it out there can science progress; being wrong sometimes is not a failure, but a necessary prerequisite of scientific progress! (Which, however, does not mean that any bogus idea is beneficial to science. It should be backed by hard data, repeatable observations, and logical deduction. See Darren Naish's blog "tetrapod zoology" for an example of what is not very helpful for science.)

So does that mean that I think we should not deal with fragmentary material any more? Also not, since that would mean that we have to ignore some 80 % of the vertebrate fossil record, and would thus loose an enormous amount of potentially important information. In the interpretation of such materials, we have made enormous progress in the past twenty to thirty years: Previously, most referrals of such fragmentary specimens was based on rather vague notions of "overall similarity", but, with the development of large data sets of anatomical characters that are typical for certain groups (so-called apomorphic characters), we can be much more specific on what basis we refer fragmentary remains to a specific clade. Of course, with incomplete material, there is always the possibility that more complete remains might prove us wrong, or that new finds or observations on other materials might show that these characters are more widely distributed than previously thought, but with this data we can formulate specific hypotheses that are then testable by such new data. There is also the danger of overinterpreting minute differences that might not be of systematic significance (for example due to individual variation or just abnormalities), but who can say when we reach this level in animals that are extinct?

As scientists, we should always remain critical. It is often said that "extraordinary claims need extraordinarily good evidence", and we are wise in remembering this when reading about the implications of interpretations of fragmentary specimens. Thus, I am not convinced that there were tyrannosaurs in the Cretaceous of the southern hemisphere, as claimed by Roger Benson and colleagues based on a single pubis. However, I am also not entirely convinced that there were carcharodontosaurids in the Late Jurassic of Tanzania, a claim made by myself on the basis of some teeth and a few vertebrae. Nevertheless, at our current state of knowledge, these are the best hypotheses to explain the available data. New finds, or new observations might prove us wrong, but such is the nature of scientific investigation.

Friday, 6 July 2012

Pterosaurs - the flying reptiles - were an important component of Mesozoic terrestrial ecosystems, yet their fossil record is strongly biased towards some exceptional localities. One of them are the Late Jurassic limestones of southern Germany. These rocks have not only yielded the first pterosaur to be described scientifically - Pterodactylus, first described by Collini in 1784, and still kept in our collections here in Munich -but, together with the famous Santana beds of Brazil and the Yixian Formation of China, they have yielded one of the most diverse pterosaur faunas in the world.

However, if you thought that we already know everything about the Late Jurassic pterosaurs from southern Germany, think again - David Hone of the University College London and his coauthors (among them once again the master of UV photography, Helmut Tischlinger) have just published a new species of long-tailed pterosaur from the laminated limestones at Brunn, eastern Bavaria. They called the new taxon, which is based on a wonderfully preserved specimen that technically belongs to our collections, though it is currently housed in Solnhofen, Bellubrunnus - the beauty from Brunn. And Bellubrunnus is not the only new pterosaur from the Late Jurassic limestones of southern Germany: Just recently, two of the authors of the new paper - Eberhard "Dino" Frey and Helmut Tischlinger - together with Christian Meyer from the Museum in Basel described the oldest azhdarchid pterosaur (the group that the giant Cretaceous forms belong to), Aurorazhdarcho, from the Solnhofen limestones, and several other new pterosaurs have recently been found.

Skeleton of Bellubrunnus. Length c. 14 cm.

Why, you may ask, is that so? Well, apart from the obvious - that pterosaur diversity was greater than hitherto recognized - this is due to a pecularity of the geological setting that is little known outside Germany: What is often lumped together as "Solnhofen limestones" actually represent several geological units that span the time from the "middle" Kimmeridgian (c. 152.5 million years ago) to the Early Tithonian (c. 148 million years ago). They thus span several million years, but so far, mainly the Solnhofen Formation has yielded abundant fossil material, including most known pterosaur specimens and the iconic Archaeopteryx. However, this is mainly due to the fact that this is the only unit that has systematically been explored in the past 200 years, since the Solnhofen slabs were the best for lithography and are also used as building materials. Nevertheless, the underlying Rögling and Thorleite formations (and their equivalents) and the overlying Mörnsheim Formation are also very fossiliferous, at least in parts. These units are now being explored more systematically, and, apart from taxa shared between the different units, we also see a lot of new species coming out. The locality that Bellubrunnus comes from, the quarry at Brunn, is thus quite a bit older than the "classical" Solnhofen limestones, and only the systematic excavations by Martin Röper of the Bürgermeister Müller Museum in Solnhofen (another one of the authors on the paper) are starting to reveal the ecosystem of that time. Likewise, a new systematic excavation in the Mörnsheim Formation at the Schaudiberg close to Mörnsheim has already resulted in the recovery of several new taxa, and in a quarry close to Wattendorf worked in by Matthias Mäuser of the Naturkundemuesum Bamberg and Winfried Werner of the BSPG the so far oldest fauna from the Late Jurassic limestones is currently being exhumed. We can thus expect many more new discoveries.

The Upper Jurassic limestone formations of southern Germany thus represent an almost unique opportunity to study the changes in a Jurassic ecosystem over a geologically short period of time. That some taxa are common to all of the different units, whereas others, such as the pterosaurs, seem to show marked differences between the faunas might indicate different evolutionary dynamics in different groups. However, it will also not be easy to tell evolutionary changes in these groups from possible effects of environmental changes between the different units. Thus, everything is known about the Late Jurassic pterosaurs of southern Germany? Far from that, the work has just begun...